Provide preliminary validation of the use of genetically engineered Salmonella strains, which specifically target solid tumors following systemic administration for use in non-invasive imaging and prodrug activation. The intent of long term research is to develop the properties of these Salmonella strains to create a targeting vector that will be a platform for the detection and subsequent treatment of tumors. The current project will perform studies to explore the signature Salmonella targets resulting in Salmonella localization in tumors. The project will also evaluate the ability of Salmonella to target to small tumor foci, metastases, and recurring tumors, as well as evaluate the targeting of Salmonella to tumors in additional murine models.